Method swizzling for all instances of class

I've been dealing recently a lot with OCMock and while is great there is some draw backs for it. The major one that I had was when I was writing integration tests for a legacy library that we have. I needed to override a method of an object that was inside a method that I was testing (so it would always return the same value). However as I didn't have that object in hand I couldn't mock it, changing the method to inject the object was a no-go because of the number of other projects that this change would have impacted so my only option was to mess around with the Objective-C runtime and inject my instance method into it so that it would override that instance method for all object of a certain type: